1. Field of the Invention
The present invention is directed to improvements in composite bearing seals having metal, such as steel, and rubber components. More particularly, the present invention is directed to a seal incorporating a Belleville type spring, wherein bonding of the embedding rubber components to the embedded spring is significantly improved.
2. Brief Description of the Prior Art
Seals for preventing ingress of extraneous material into the interior bearing structure of the rotating roller cones of rock bits have been known in the art for a long time. These seals also serve the function of preventing the loss of lubricant from the interior of the bearing.
One type of rock bit seal structure includes a metal, Belleville type spring which is embedded in rubber or rubber-like material, and forms sealing surfaces coming into contact with the respective sealing surfaces of the journal and rotating roller cones of the rock bits. Such rock bit seals having the basic Belleville spring type structure, and several improvements and variations of such structures are described, for example, in U.S. Pat. Nos. 3,381,968; 3,489,421; 3,199,878; 3,680,873; 3,137,508, and 3,370,895.
U.S. Pat. No. 3,370,895, the specification of which is expressly incorporated herein by reference, particularly describes a bearing seal having an annular Belleville type spring embedded in rubber, and an annular retaining ring which is in metal-to-metal contact with the journal leg of the rock bit. The rubber embedding the spring is also bonded to the retaining ring. This patent is of interest to the present invention, because the basic structure of the preferred embodiment of the present invention, although having greatly strengthened metal-to-rubber bond, is quite similar to the seal structure described in the patent.
In this regard it is noted that a significant requirement for satisfactory operation of rock bit seals of the above-noted type, i.e. of seals which include a Belleville type seal and an embedding rubber material, is for the rubber to remain strongly bonded to the metal for a prolonged period of time, even during the harsh "downhole" operating conditions of the rock bit. The present invention provides a very significant improvement over the prior art in this regard.
U.S. Pat. Nos. 4,299,640; 4,333,785; 4,465,547; 3,416,975, and 1,954,403 are of interest, as further background to the present invention, because these patents relate, generally speaking, to the technology of bonding non-metallic materials to metals. U.S. Pat. No. 4,465,547 discloses a structure wherein polyvinylidene fluoride (PVF.sub.2) is bonded to a metallic substrate by an adhesive, the PVF.sub.2 having been subjected to a step of plasma etching prior to the application of the adhesive.